Merge pull request #4508 from jpbetz/client-go-context-ga

Mark client-go context as stable to match GA criteria in KEP

Author: k8s-ci-robot

keps/sig-api-machinery/1601-client-go-context/kep.yaml

@@ -15,4 +15,4 @@ last-updated: 2020-01-23
 status: implementable
 
 latest-milestone: "1.18"
-stage: "beta"
+stage: "stable"